Hi Roshan,

The syllabus of jee has remained the same from many years but the pattern and difficulty level has changed with each year. But there are some topics from which questions do come always

For example- organic chemistry, rotational motion , differential equations.

Start preparing from NCERT first then practice questions from other books like 

For JEE mains DC Pandey, RD Sharma objective, GRB for chemistry.

Do solve the previous year question you will get to know about the level of difficulty.

Wishing you luck for future. For any other query do comment me below.